1. Field of the Invention
The present invention relates to a profile extracting method and system for identifying a shape of an object from a two-dimensional image having shape information of the object, preferably usable in modeling of a three-dimensional shape of the object.
2. Description of the Related Art
Using a photograph of an existing object, modeling for specifying the shape of the object is executed. Disposing a photograph and a primitive in a virtual space, the primitive is moved or deformed so that the projected image oil the photographic plane may coincide with the object image in the photograph. It is preferred for the job efficiency to set up a modeling system in which the user is responsible for rough modeling and the system is responsible for fine adjustment. For fine adjustment, the outline profile of the object must be extracted from the photograph as accurately as possible.
In image analysis by computer, when recognizing the shape of an object expressed by an image, according to a general method, the edge in the image (the portion of evident change of pixel value) is detected, and detected edges are linked to extract the profile of the object. The edge is detected by calculating the edge intensity of pixel by applying a local operator as represented by differential type to the pixel. Usually, to decrease the effects of noise components of the image, the pixel of which edge intensity exceeds a predetermined threshold is detected as edge.
Hitherto, being susceptible to effects of noise components, for example, even if the actual profile is composed of a set of lines such as straight line and arcs that can be expressed by simple numerical formula, the extracted profile was often composed of complicated lines. Or the extracted profile of object was a line (curve or straight line) precisely conforming to the edge distribution. Accordingly, the shape of the object cannot be identified correctly if the object to be extracted and other object are partly overlapped in the image, that is, if the profile to be extracted and profile of other object are continuous.